Air or gas blast electric circuit breakers



Feb. 26, 1963 A. RoxBuRGH ETAL 3,079,534

AIR OR GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed March 7, 1950 5 Sheets-Sheet 1 ALBERT ROXBUBGH ALBERT LEIGH JERROLD JOSEPH FELLERMAN Feb. 26, 1963 A. ROXBURGH ErAL 3,079,534

AIR CR CAs BLAST ELECTRIC CIRCUIT BREAKERS Filed March 7, 1960 5 Sheets-Sheet 2 M ENTETE ALBERT ROXBURGH ALBERT LEIGH JERRQLD JOSEPH FELLERMAN Feb. 26, 1963 A. ROXBURGHAETAL 3,079,534

AIR OR GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed March "L 1960 5 Sheets-Sheet 3 INVENTORS ALBERI ROXBURGH' ALBERT LEIGH JERROLD JOSEPH FELLERMAN Feb. 26, 1963 A. RoxBURGH ETAL 3,079,534

AIR OR GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed March 7. 1960 5 Sheets-Sheet 4 ALBERT vROXBURGH ALBERT LEIGH JERROLD JOSEPH FELLERMAN BY anni Qm/ Feb. 26, 1963 A. ROXBURGH ETAL 3,079,534

AIR OR GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed March 7, 1960 5 Sheets-Sheet 5 I l III! wx y United States Patent O Y 3,079,534 g AIR 0R GAS BLAST ELECTRXQ CIRCUIT *.f .-BREAKERS'- i Albert Roxhurgh, Londen, Aibert Leigh, Kenton, Harrow, and 7Jerrold Joseph Fellerman, London, England, assignrors tofAssociated Electrical Industries Limited, London,

Engiand, a British company Y v c Filed Mar. 7,1960, Ser. No. 13,276 Claims priority, .application Great Britain lidar. 9, 1959 19 Claims. (Cl. S17- 59) I This invention relates to air or gas blast electric circuit breakers. L l

The term. gas as usedthroughout-the preamble of this specication and in the claims appended thereto includes by definition, air. i

Avgas blast breaker commonly has in each phase a gas ,receiver and currentinterrupting contacts, the num'- ber of sets of which contacts depends on the volta-ge at which the breaker is. designedto work. The contacts are separated by a gas blast which is admitted from the gas 'receiver through blast control valves to the interrupter heads carryingfthe contacts.

According to the present invention a gasblast electric circuit breaker comprises in a phase, a gas receiver,

atleast two sets of serially connected circuit'interrupterv contacts Viny which means are .provided for a manually initiated separation of less than the full number ot sets of ser-ies contacts available for automatic operation of the breaker. v s

Conveniently, one half of the number ofv sets ofV contacts operablel on an .automatic operation are operable on the manually initiated operation.

/IPrefera-bly, time delay means are provided whereby after operation of the meansr provided for. the lmanual operation, the rest of the serially connected contacts are opened simultaneously or in two or more successive stages. c

The invention is of application in opening a small value of electric current in a highly inductivey circuit, such asa transformer primary circuit whose secondary is on lopen ycircuit or is loaded with reactors. -Bymeans of the invention the over voltagedue to current chopping to zero (Le. decreasing suddenly to zero) lwill be limited by restriking across theV initially opened contacts .whose withstand-voltage, i.e. that voltage at which those gaps will rcstrike will be less than that of the full number of gaps employed for the automatic opening.

YThe means provided for the manually initiated operation of less than the full number of contacts may conveniently comprise an vadditional blast valve not operable on automatic operation, or means whereby one of the blast valves voperableron automatic operation is initially independently operable lon the manual operation either by independent operation of separate parts of an operating shaft or by initial operation of means movable relative to a single operating shaft.

These and other features of the invention are more fully hereinafter set forth in the specification and in the claims appended thereto. v l

Three embodiments of the invention .will now be described with reference to the accompanying drawings in which,

FIG. l is a schematic view of part of one embodiment,

PIG. 2 is a side view from the left of FIG. 1 of the rest of the embodiment,

FIG. 3 is a fragmentary schematic view of an alternative embodiment,

lFIG. 4 is a complete schematic of still another embodiment, and y f .FlG.` 5 is a schematic viewo'f the top part ofthe breaker of FIGS. 1 3.

y, 3,079,534 Patented Feb. 26, 1963 for operating one blast control valve -41 independently of the other blast control valve 42.

For -the purpose-of illustration only, the circuit breaker. OLPIGS. .l and 2 isof the seal-ott type. Such a breaker. .is .itself well known and avoids the use of a sequential switch additional to. the circuit `interrupter contacts. .This is ,achievedby the chamber 201, FIG. 5 containing the contacts 202 and 203, FIG. 5 having an exit which .after interruption of the circuit is closed so that the'pressure gasmaintains lthe separation of the contacts and the circuit isolated. Reclosure of the contacts is provided by vdumping the air in the contact chamber to atmosphere` f The control .valves 4 1 and 42 are mounted in the air receiver 40 and are assemblies of generally cylindrical form with pipes 43 and 44 leading to support insulators 20S and 206, FIG. 5 carried by the air receiver 40 and each' carrying a double breaker headserially connected in line 207. VThe blast control valve assembly'41. has entry ports.,45 closed by a piston 46. An operating rod 47 for the piston 46 havingv a flange 47 resting on the piston 46 extends freely through the piston v46 and is pivotally connected at 47' to an arm 48 rigidly carried by the operating shaft 49. vThe piston46 prevents entry of air fromv the air receiver 40 through ports 4S to the pipe 43. The blast control valve assembly 41 also includes a pressure-operable 'piston 50 biassed to the position shown bya coil spring 51 to seal off exit ports 52.

The blast control Yvalve assembly 42 is of substantially the same` construction as assembly 41 as so far described, the like parts in assembly 42 being suiiixed a. The operating rod 47a of assembly 42 is however secured to the piston146a. The rod 47a is connected via an arm 48a with the operating shaft 49 in the same manner as is .the rod `47. The operating shaft 49 is mounted for rotation in bearings, not shown). An arm 53 is rigidly secured 4to theshaft 49 and pivotally connected at 54 (FIG. 2) to a rod 55 biasedY to the right hand y(in FIG. 2) by an opening spring 56 of coil form operating on an end piece 57 on the rod55. The arm 53 is held in the position illustrated (FIG. 2) against the bias of the spring S6 by atrip-free linkage.

The linkage comprises a link 58 pivotally connected t0l arm 53 at-54 and pivotally connected at 59 to a short arm 60 of a bell crank lever 61 which is itself rotatable about a fixed pivot at'62. A longer arm 63 of the bell crank lever 61 is pivotally connected at 64 to a link 65 pivotally connected at 66 to link 67. The links 65 and 67 together act as a collapsible strut preventing bell crank 6l from rotatingv anti-clockwise from the illustratedposition. This is achieved by arlink 68 pivotally connected to links and 67 at their pivot 66 and by the pivoted connection .of thelink 67 at 67 to a latched rod 82 of a closing cylinder 83. The link 68 is pivotallyr connected at 69 to links 70.and.72. Link 70 is rotatable about a fixed pivot ,71 butis prevented from rotating anti-clockwise (in FIG. 2).by pivotal, connection of the link 72 at 73 to a lever 74 which is itselfpivoted at 75 and carrying a roller at 76.y A latch member 77 pivotedat 77' prevents the'lever 74 rotating clockwise (in FIG. 2). A trip coil 78 is positionedadjacent the latch 77 and is energisable through leads 80, 81 from a trip supply (not shown). The rodf8'2 has a tlange 84 within the cylinder 88 and a flange 85 outside the cylinder and the rod 82 is held in the illustrated position by means of a latch 86 pivotedat aV fixed pivot 87 and acting on the 'flange 85.

3 The'latch 86 is biased't'o the left hand (in FIG. 2) by acoil spring 88.

The closing cylinder S3 has a piston 89 fed by entry passage 96 from a servo valve cylinder 95 of the servo valve assembly 95. The servo valve assembly is of the pressure diiierential type. Such valves are well known in the switchgear art. The servo valve cylinder contains a piston 97 biased by a coil spring 98 to the left hand (in FlG. 2) to close an entrance 96 to passage 96. An electromagnetically operable pilot valve 99 is biased to the right hand by a spring 100 to close exit port 99. rEhe pilot valve 99 has an operating coil 101 energisable from a breaker closing electrical supply through leads 101V and 101". Pressure air is connected to the servo valve cylinder 95 from the air receiver 40by means of a pipe 162. Pressure air leaks through a restricted passage 97 in the piston 97 and the piston is maintained in the illustrated position by the sum of the .forces due to the spring 9S and the pressure behind the piston i.e. on the right hand side (in FIG. 2) acting against air pressure tending to move the piston to the right. Pilot valve A99 prevents the air pressure behind the piston from escaping to atmosphere through 99. Theclosing'piston 89 closes in the illustrated position an entrance 90 to a pipe 91 leading from the closing cylinder 83 to a pneumatic safety switch 92 comprising piston 93 operable in cylinder 92 and biased to the left (in FIG. 2) by a coil spring 94. The piston 93 carries a bridging contact 93.

The blast control valve assembly 41 includes a means for operating the piston 46 independently of the rod 47 i.e. independently of piston 46a of the valve assembly 42. The operating shaft 49, arms 48 and 48a, rods 47 and 47a and the trippable linkage 58, 61, 65, 67, 65, 70, 72 and 714 remaining in the illustrated position. The means just referred to comprise a tube 103 fixed to piston 46 and surrounding the rod 47 and the tube is held in the illustrated position (FIGS. 1 and 2) by means of a prop 104 positioned underneath (in the figures) a flange 105 of the tube 103. The prop 104 is pivoted at 106 on the arm 43 and at 10S to a link 107. The link 107 ispivoted at 109 to a' long arm 110 of a bell crank lever 111 rotatable about a fixed pivot 112.Y A shorter arm 113 of the bell crank 111 is pivotally connectedat 114 to a rod 115 connected with a piston 116 contained in a cylinder 117 and biased to the right (in FIG. 2) by a coil spring 118".

The rod 115 carries a contact 119 bridging contacts 120,

121. The cylinder 117 is connected by means of an air supply pipe 125 with a cylinder 126 of a servo and pilot assembly 126. The servo valve 126 is of the pressure diiierential type operating in the same manner as servo valve 95'. The cylinder 126 is connected via pipe 130 with the air receiver 46. A servo piston 127 is biased upwardly (in FIG. V2) to close an entry port. 129 of the pipe 125. Leakage air pressure entering through restricted passage 127 in piston 127 is retained behind the piston 127 by an electromagnetically operable pilot valve 132biassed by a spring 133 to close exit port 132. The pilot valve 132 has an operating coil 135 connected in circuit with contacts 120, 121 and 119 by leads 122 and 123. A restricted pipe 136 leads ot the pipe 125 into a cylinder 137 of a pneumatic auxiliary switch 137' which ,contains a piston 133 biassed tothe right (in PIG. 2) by a coil spring 139. The piston 138 carries a bridging contact 141 for bridging normally open contacts 142, 143. The latter contacts are connected in circuit with' a battery .1145 the trip coil 78, normally closed contacts 147, 143 and 149 and normally closed contacts 93', 151, 152 by means of electrical leads 144 and 144', 8G, 81, 156', 150 and 146. 'l .e contact 147 closed in the illustrated position is movable to open contacts 148, 149 on movement oi' the bell crank 61 anti-clockwise (in FIG. 2), vand theA neous operation ci the blast control valves 41 andj42 byl energization of the trip coil '76. The latch 77 is pivoted Vclockwise (in FIGfZ) by the trip coil 78 to release the lever 74 so that the coil spring 56 can rotate the shaft 49 and lower rods 47 and 47a. Links 104 and 107 retain the relative positions illustrated but are lowered with the arm 43 bell crank 111 is rotated clockwise. The lever 74 is rotated clockwise about its pivot 75 allowing the pivot 69 to be moved by the spring V56 to the right and downwardly (in FIG. 2) under the control of link 70. The pivot 64 and the bell crank lever 61 are moved anti-clockwise (in FIG. 2) about the pivot 62. The flange 85 is initially retained inthe illustrated position by the latch E56 so that the included angle between link 65 and 67 decreases and an end 68 of link 63 pushes the latch S6 clockwise about its pivot 87. When the link 66 has moved suiiiciently downwardly and to the right (in FlG. 2) the latch 86 clears the iiange 85 so that the rod 82 is moved down wardly until the iiange 814 is adjacent the closing piston S9. As this occurs that part of the linkage consisting of pivot 69 is as shown in FIG. 2 but its pivot 66 is lowered so that the link 6d slopes downwardly (in FIG. 2) from`v 69. The contacts 147 are moved away from contacts`145, 149 by the rotation of the bell crank 61.

The downward pull on the rods 47 and 47a lowers the pistons 46 and 46a' (FIG. 1) 'so that the latter uncover the ports 45 and 45a to admit air pressure to the pipes 43, 44 to separate the available interrupting contacts of the breaker. The pistons 46 and 46a seat on parts `155 and 155e of the valve assemblies 41, 42 so as to close yrestricted passages 156 and 156e leading to top surfaces FIG. 2) against the bias of the spring 98. Movement of of the pressure pistons 50 and 50a. The circuit breaker being of the seal-oit type the air pressure now holds thecontacts apart and the circuit isolated as has hereinbefore been explained. In order to reclose the circuit breaker' the closing coil 101 is energised (automatically in theI case of auto-reclosing) to move the pilot valve 99 away from its port 99 to allow air pressure on the right hand side of piston 97 to exhaust to atmosphere so that the air supply from pipe 102 moves the piston 97 to the right (in the piston 97 to the right allows the pressure air to enter the space under the piston 89 through passage 96 so as to raise piston 89. The flange 84 and rod S2 'are moved upwards to the illustrated position and so that the flange S5 is relatched by the latch 86. The reset links 70, 72 hold pivot 69 in the illustrated position so that the links 67 and 65 act as a strut pushing the long arm 63 of the bell crank clockwise to the illustrated position. vIhe links 58 and 55 and arms 53 are returned to the illustrated position and the shaft 49 rotated to raise arms 4E and 48a. Rods 47 and 47a and the pistons 46 and 46a of theV operable valves 56 and 56a to open ports 52 and 52a to exhaust pressure in the columns and chambers to atmosphere so that the contacts reclose.4 i

Itis to be understood thatports 45 and 45a are re closed before ports 52 and 52a are opened by valves 56-` Y and 56a.

Attention is directed to UK. patent application 6978/59 which claims and describes such blast control valves.

It it is desired to Vmanually open a highly inductive circuit i.e. one where only a low value of current flowsthen in the first instance (as explained hereinbefore) only one blast valve namely 41 is operated. The valve 42 is operated thereafter with a time delay. This is provided toras follows: rIhe trip coil is energised to lift the pilot valve 132 so as to allow air on the under sidev oi the aorasea acting on links il and l2. The other ends (ie. the upper ones in FIG. 4) Vare connected together through a trippabie linkage i3, lli, l5, 16, i7, iii and latched at i9 (in the illustrated position). A tripping coil @a is arranged adjacent the latch llt for releasing the latter.

A lever E@ pivoted at 232i is pivotally connected at 2.7i to the link lli/i., at 2e to an operating rod 2d or" a piston 2S acting in cylinder 25a communicating through conduit 25h with the low pressure side ot control valve 2, and at 2o to a link 27 which is pivotally connected to a bell crank lever 23 latched at 29 (in the illustrated position). A trip coil is arranged adjacent the latch for releasing the latter. An energising circuit of the trip coil 2;@ includes normally open contacts Sha which are under the control of a piston El acting against a spring Sla in a cylinder 3:2 communicating thro-ugh conduit 33 with the low pressure side of the control valve l.

in order to open a small value of current in a highly indicative circuit a switch (not shown) is Amanually closed to energise the trip coil lilla so as to release the latch i9 to allow the spring 9 to turn half shai't 3 and open the control valve i; so as to open the current interrupting contacts associated with said control valve. The control valve 2 is not opened at this stage so that the circuit has one half of the breaks which would be present on an automatic opening.

Pressure air which has passed through the control valve l and the conduit 33 causes the piston 3l to move against its spring 3io to close the contacts 30a to complete an energising circuit through the trip coil Sti so that the latch 29 is released. The spring l@ turns the half shaft i to open the remaining control valve 2 and so opens the remaining current interrupting contacts in the inductive circuit.

, The release of spring l@ and the rotation of shaft 4 causes arm 3 to pull upon link 13 of the trip linkage 13, liti, T15, lo, 17, and 1S so that the linkage is relatched at 19. Y

The opening of the blast valve 2 allows air pressure to pass through conduit 25h to the cylinder 25a so that the piston 25 acts through the rod 24 upon lever 2t) so as to compress the spring 10, the spring 9 also being compressed because the arms 7 and 8 move together due to their connection by links 13 and 14 which are prevented from collapsing by the resetting of the trip linkage so that it is latched at 19.

Movement or" the lever Ztl also resets the trip linkage 2'7, 2% so that it is relatched at 29 whereby when the blast valve 2 closes and pressure air is cut oft from the piston 25, the springs 9 and itl remain compressed. On automatic operation, the trip coil 30 only is energised and releases the trip linkage 27, 28 so that both the shafts Vis and 4 are rotated by the springs 9 and it).

The blast valves l and 2 are of differential design and are arranged to reclose automatically when the auxiliary or servo valves la and 2a return to the sealed position and pressure air builds up on the spring sides of the blast valves. The blast valves open when the arms S and d push open the servo valves la and 2a thus allowing discharge of air pressure to the atmosphere on said side of the valves.

Although a partly electrical link has been shown between blast valve it and latch or prop 29 it should be appreciated that air pressure could be used directly to unlatch 219 with the appropriate time delay after control valve l has opened.

Whilst these embodiments have been described as arr operated they may be operated by any suitable gas.

` Whilst in these embodiments half the available contacts are initially operated on the manual operation the invention is not limited in this respect, any number of the available sets of contacts can initially be opened and the remainder be opened in one Yor more subsequent stages. As many stages as there are sets of contacts may be employed. In one example where four circuit breaker double-break heads are arrangedin series i.e.. four pairs of sets of contacts each pair having a separate blast control valve each of which valves may be operated sequently so that one pair of sets of contacts are opened in each of four successive stages until all eight contacts are opened.

Modication of FlG-S. l and 2 to provide more stages merely needs further blast valves like lil and further sets o' interruptor contacts supplied by the respective valves. instead of contacts 1.4i and M2 being arranged to energise the trip coil 7? they will energise a further partial tripping coil like i335 to operate mechanisms like 126', 137', il?, lili, lil?, lltili, and for each of the further blast valves. The last stage is operated by the connection of contacts like 1.42 and M3 to energiseV coil 73. The last blast contr-ol valve will be like blast control valveliZ.

vWhat We claim is:

l. A gas blast electric circuit breaker comprising in a phase, at least one gas receiver, at least two sets of serially connected circuit interruptor contacts, at least two blast valves for controlling access of gas :from the receiver to the contacts, means for automatically initiating simultaneous opening of all said blast valves in response to a fault thereby to simultaneously open lall said contacts, and means for opening less than the full number of blast control valves on a manually initiated operation of the circuit breaker such that the remaining blast control valves a least initially remain closed and at least-` initially less than the full number oi contacts are opened.

2. A gas blast electric circuit breaker as claimedin claim l, in which time delay means are provided whereby after operation of the mean-s provided for the manual operation, the rest of the serially connected contacts are opened.k

3; A gas blast electric circuit breaker as claimed in claim 2, having pneumatically operable means and means for connecting pressure gas from the contact side of an initially operated blast control valve with the pneumatically operable means for initiating the Operation of at least one of the remaining available blast control valves in the phase with said time delay.

4. A gas blast electric circuit breaker as claimed in claim 3, having a trip coil energizing circuit for operating the said one of the remaining valves and a switch having contacts arranged on operation of the switch by the pressure gas to complete said energizing circuit for operating said further blast valve.

5. A gas blast electric circuit breaker as claimed in claim l, having an operating shaft for the blast control valves and operating rods connecting the valves to the shaft, said initially -operable valve on manual operation having means arranged to move as one with the rod on automatic operation and on the manually initiatedoperation to be moved relative to the rod in order to operate the initially operated blast control valve only.

6. A gas blast electric circuit breaker as claimed in claim 5, having a tube surrounding the rod and a latch preventing movement of the tube relative to the rod in the closed position of the blast control valve and means Vwhich on the manually initiated operation unlatches the tube and moves it with respect to the rod;

7. YA gas blast electric circuit breaker as claimed in claim 6, having a lever and a collapsible linkage connected to the lever whereby movement of the lever with the rod stationary collapses the linkage and moves the tube.

8. ln a highly inductive electric circuit having a small value of electric current an electric gas blast circuit breaker as claimed in claim l, wherein on the manually initiated operationthe overY voltage due to the sudden reduction to zero value of the current is limited by restriking across the initially opened contacts.

V9. ln the highly inductive Yprimary circuitY of a transv former whose secondary is loaded with reactors an electric gas blast circuit breaker' as claimed in claim 1, wherein on the manually initiated operation the over vol-tage due to the sudden reduction to zero value of the current is limited by res-triking across `the initially opened contacts.

10. A gas blast electric circuit breaker as claimed in claim 1, in which the remaining sets of contacts are arranged to open in more than one stage of at least one set at a time with successive time delays between stages, 'the means provided for Ithe manually initiated operation are arranged to initiate automatically Ioperation of Ithe next stage of at least one set of contacts with the required time delay by actuating like means as are actuated at the beginning of 4the manual operation until in the last bu-t one stage energization of a trip coil enengizable on automatic operation is initiated to open the last stage of at least one set of contacts.

11. A gas blast electric circuit breaker comprising in a phase, at least one gas receiver, at least two sets of serially connected circuit interrupter contacts, at least one blast valve for controlling access of gas from the receive-r to the contacts, means for automatically initiating opening of said blast valve in response to a fault thereby .to simultaneously open all said contacts, at least one further blast control valve for controlling gas access from the receiver to less than the full number of contacts and inoperable on response of the circuit breaker to the fault, and means for opening said further blast control valve on a manually initiated operation of the circuit breaker such that 'the iirst referred -to blast control valve at least initially remains closed so that at least initially less than the full number of contacts are opened.

12. A gas blast electric circuit breaker as claimed in claim 11, having a bla-st valve operating shaft in at least two separate parts and Ia trippable linkage mechanism interconnecting said parts and arranged on yautomatic operation of the breaker so that the parts of the shaft are rotated as one while on the manually initiated operation one only of the parts of the shaft is initially operated, the other part being operated after a time delay.

-l3. A gas blast electric circuit b-reaker as claimed in claim l2, in which the linkage includes means arranged to reset the linkage after tripping of the linkage and opening of the remaining valve and a single resetting spring being employed for resetting the parts of the shaft and reclosing the breaker.

14. A gas blast elect-ric circuit breaker as claimed in claim 13, having a trip coil energizing circuit for operating the said one of the remaining valves and a switch having contacts arranged on operation of the switch by pressure gas to complete said energizing circuit for operating said further blast valve.

15. A gas blast electric circuit breaker as claimed in claim 12, having pneumatically operable means and means for connecting pressure gas from the contact side of an initially operated blast control valve with the pneumatically operable means for initiating the operation of at least one of the remaining available blast control valves in the phase with said 4time delay.

16. In a highly inductive electric circuit having a small value of electric current an electric gas blast circuit breaker as claimed in claim 1l, wherein on the manually initiated operation the over voltage due to the sudden reduction -to zero value of the current will be limited by restriking across the initially opened contacts.

17. In the highly inductive primary circuit of a transformer whose secondary is loaded with reactors an electric gas blast circuit breaker as claimed in claim ll, lwherein on the manually initiated operation the over voltage dueto the sudden reduction to zero value of the curent is limited by restriking across the initially opened contacts.

18. A gas blaat electric circuit breaker as claimed in claim ll, in which the remaining sets of contacts are arranged -to open in more than one stage of at least one set at a time with successive time delays between stages, the means provided for the manually initiated operation are arranged to initiate automatically operation of the next stage of at least one set of contacts with the required time delay by actuating like means as are actuated at the beginning of the manual operation until in the last but one stage energization of a trip coil energizable on automatic operation is initiated to open the last -stage of at least one set of contacts.

19. A gas blast electric circuit breaker as claimed in claim ll, in which time -delay means are provided for opening the rest of the serially connected contacts after operation lof the means provided for -the manual operatien.

References Cited in the file of this patent UNITED STATES PATENTS 2,918,588 Rittenhouse et al. Dec. 22, 1959 

1. A GAS BLAST ELECTRIC CIRCUIT BREAKER COMPRISING IN A PHASE, AT LEAST ONE GAS RECEIVER, AT LEAST TWO SETS OF SERIALLY CONNECTED CIRCUIT INTERRUPTER CONTACTS, AT LEAST TWO BLAST VALVES FOR CONTROLLING ACCESS OF GAS FROM THE RECEIVER TO THE CONTACTS, MEANS FOR AUTOMATICALLY INITIATING SIMULTANEOUS OPENING OF ALL SAID BLAST VALVES IN RESPONSE TO A FAULT THEREBY TO SIMULTANEOUSLY OPEN ALL SAID CONTACTS, AND MEANS FOR OPENING LESS THAN THE FULL NUMBER OF BLAST CONTROL VALVES ON A MANUALLY INITIATED OPERATION OF THE CIRCUIT BREAKER SUCH THAT THE REMAINING BLAST CONTROL VALVES A LEAST INITIALLY REMAIN CLOSED AND AT LEAST INITIALLY LESS THAN THE FULL NUMBER OF CONTACTS ARE OPENED. 